In recent years, a pressure-reducing valve for reducing a pressure of a fluid flowing in a flow passage, and an on-off valve for opening and closing the flow passage to control the fluid flowing in the flow passage have been practiced.
FIG. 10 is a cross-sectional view schematically showing a pressure-reducing valve 2 including a seat portion 1 according to a first prior art. FIG. 11 is an enlarged cross-sectional view showing the seat portion 1. The pressure-reducing valve 2 comprises a housing 3, a piston 4, the seat portion 1, and a spring member 5. The housing 3 is provided with a primary port 6 and a secondary port 7. The cylindrical piston 4 is displaceably inserted into the housing 3 in an axial direction of the housing 3. In the piston 4, an intermediate portion and a first end portion in the axial direction are retained in the housing and a second end portion in the axial direction is faced to the primary port 6. A connecting hole 8 is provided in the piston 4 to connect the primary port 6 to the secondary port 7. A valve body element 9 of a circularly annular shape is provided at a second axial end portion of the piston 4 so as to protrude in the axial direction. The seat portion 1 on which the valve body element 9 is pressed is fixedly attached to the housing 3 so as to surround the primary port 6. The valve body element 9 and the seat portion 1 form an orifice 10. The orifice 10 separates an interior of the housing 3 into a primary-pressure chamber 11 connected to the primary port 6 and a secondary-pressure chamber 12 connected to the secondary port 7. The piston 4 is provided with a spring member 5. The spring member 5 applies a spring force to the piston 4 in a first axial direction. The pressure-reducing valve 2 reduces a pressure of the fluid supplied to the primary port 6 by flowing it through the orifice 10 and outputs the operative fluid from the secondary port 7.
FIG. 12 is an enlarged view showing a seat portion 1A according to a second prior art. The seat portion 1A is provided at the pressure-reducing valve 2. The seat portion 1A is fitted to the housing 3 in such a manner that the seat portion 1A surrounds the primary port 6 and the valve body element 9 can be pressed thereon (for example, see patent document 1).
FIG. 13 is an enlarged view showing a seat portion 1B according to a third prior art. The seat portion 1B is provided at the pressure-reducing valve 2. The seat portion 1B is fitted to the housing 3 in such a manner that the seat portion 1B surrounds the primary port 6 and the valve body element 9 can be pressed thereon. The seat portion 1B is retained by cooperation of a fixing member 13 made of a metal material and the housing 3.
Patent document 1: Japanese Laid-Open Patent Application Publication No. 2005-23975